1. Field of the Invention
Embodiments relate to a thin film transistor, a display device including the same, and associated methods.
2. Description of the Related Art
A thin film transistor (TFT) may include an active layer with a channel region, a source region and a drain region, and a gate electrode on the channel region. The gate electrode may be electrically isolated from the active layer by a gate insulating layer. The active layer of the TFT described above may generally include a semiconductor material, e.g., amorphous silicon or polysilicon. However, if the active layer is formed of amorphous silicon, mobility may be low, so that it may be difficult to operate a driving circuit at high speed. On the other hand, if the active layer is formed of polysilicon, mobility may be high, and a threshold voltage may be non-uniform. Therefore, a separate compensating circuit may be necessary.
In a conventional method of fabricating a TFT using low temperature polysilicon (LTPS), a high-cost process, e.g., a laser heating treatment, may be used. In addition, it may not be easy to control characteristics. Therefore, it may be difficult to apply the conventional method of fabricating a TFT using LTPS to a large-area substrate.
In order to solve these problems, an oxide semiconductor as an active layer has been considered. An oxide semiconductor using zinc oxide (ZnO) as a main element is thought to be an amorphous and stable material. If such an oxide semiconductor is used as an active layer, a TFT may be fabricated using a conventional LTPS process, and the LTPS process may be performed at a low temperature, e.g., about 300° C. or less. However, in order to use an oxide semiconductor in a TFT device, a process that satisfies and improves electrical characteristics may be required.